The most common and most likely answer to this crossword clue is the 9 letter word ACADEMIES
I've seen this crossword clue in The Times
A
C
A
D
E
M
I
E
S
More clues leading to the result ACADEMIES
Buddy explains!
The straight part
We know that "alternatives for comprehensives" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case alternatives for comprehensives = academies.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ACADEMIES mean?
ACADEMIES noun- (usually capitalized) The garden where Plato taught.
- (usually capitalized) Plato's philosophical system based on skepticism; Plato's followers.
- An institution for the study of higher learning; a college or a university; typically a private school.
- A school or place of training in which some special art is taught.
- A society of learned people united for the advancement of the arts and sciences, and literature, or some particular art or science.
- The knowledge disseminated in an Academy.
- (with the, without reference to any specific academy) Academia.
- A body of established opinion in a particular field, regarded as authoritative.
- A school directly funded by central government, independent of local control.